1. Field of the Disclosure
The invention relates to a head mounted display device, in particular, to a head mounted display device with a detachable image display unit.
2. Description of the Related Art
Various Head Mounted Display devices (hereinafter interchangeably referred to as “HMDs”) have been commercialized as portable displays for television, games and personal digital assistants (“PDAs”). In a known HMD, e.g., the HMD disclosed in Japanese Published Unexamined Application 2007-148131 (hereafter interchangeably referred to as “JP 2007-148131”), an eyeglass type HMD is disclosed as an example of HMD. In the eyeglass type HMD, an image display unit is disposed in front of a frame of the eyeglass type HMD such that the image display unit is adjustable in a right-and-left direction. An adopter member, in which a permanent magnet is embedded, is detachably disposed in the upper edges of both a left rim and a right rim that support lens of the eyeglass type HMD. A rail is fixed to the adopter member by the permanent magnet, and a retaining shaft is movably disposed in the rail. The image display unit is fixed to the frame via a holding ring. The holding ring surrounds the image display unit and is fixed to the retaining shaft by a screw nut.
In another known HMD, e.g., the HMD disclosed in U.S. Pat. No. 6,204,974 A (hereinafter interchangeably referred to “U.S. Pat. No. 6,204,974”), another eyeglass type HMD is disclosed. In the eyeglass type HMD, a housing assembly for housing an image display unit is retained in a temple of a frame of the eyeglass type HMD by a clamp assembly that includes a mounting fixture and a clamp. A pair of pins extend from the mounting fixture that is retained in the housing assembly. The pair of pins penetrate the temple from the outside of the temple, and the housing assembly is retained in the temple.
In the eyeglass type HMD disclosed in JP 2007-148131, the image display unit is retained in the frame by retaining means such as the retaining shaft that extends downward from the upper edges of the left rim and the right rim. The retaining means such as the retaining shaft would interrupt a user's front view when the user's view moves from images, displayed on the image display unit, to a large display or document in front of the user.
In the eyeglass type HMD disclosed in U.S. Pat. No. 6,204,974, the housing assembly is retained in the temple. When the frame is mounted on the user, the temple would deform according to the shape of the user's head. The deformation of the temple may shift the position of images displayed on the image display unit.